1. Field of the Invention
This invention is directed to a method and apparatus for healing wounds. More specifically, to a method and apparatus for healing wounds by an application of low frequency microelectric current.
Chronic wounds and skin ulcers are, typically, contaminated with a variety of microorganisms, both pathogenic and non-pathogenic types. The non-pathogenic types of microorganisms constitute the normal flora of intact skin and may become pathogenic when their numbers overwhelm the natural host defenses in the wound environment and subsequently cause infection. Becker, G. D.: "Identification and Management of the Patient at High Risk for Wound Infection". Head Neck Surg Jan/Feb: 205-210, 1986.
Quantitatively, it has been shown by Kucan, J. O. et al in "Comparisons of Silver Sulfadiazine and Physiologic Saline in the Treatment of Chronic Pressure Ulcers", Amer Ger Soc 29:232-235, 1981, that open wounds can maintain a bioburden of approximately 10.sup.5 microorganisms per gram of tissue without clinical manifestation of infection. However, a bioburden of greater than 10.sup.5 is a significant challenge for the local wound tissue defenses. Consequently, a bioburden of 10.sup.6 microorganisms per gram will often result in wound infection. Robson, M. C. et al., "Bacterial Quantification of Open Wounds", Military Medicine 134:19-24, 1969.
Wounds that are heavily contaminated by microorganisms, but not clinically infected, are often characterized by a prolonged period of inflammation as well as a delay in wound repair and healing. Micro-organisms that contaminate wounds have been implicated as an important factor in the retardation of wound healing by interfering with leukocyte phagocytosis and also by the depletion of nutrients and oxygen required for normal tissue granulation. Ree, B. R. et al., "Cutaneous Tissue Repair: Practical Implication of Current Knowledge, Part II", Journal of the American Academy of Dermatology 13(6): 919-941, 1985.
Historically, wounds have been cleansed and disinfected with a host of different types of antiseptic agents ranging from acetic acid to halogen-based solutions such as complexed iodine. While topical antiseptic agents have the recognized ability to either inhibit or destroy infection producing microorganisms, they also induce chemical trauma and necrosis of the host defense cells, such as macrophages, when used directly in the wound site. Branemark, P. I. et al., "Tissue Injury Caused by Wound Disinfectants", Bone Joint Surg Am 49:48-6.2, 1967 and Lineweaver, W. et al., "Topical Antimicrobial Toxicity", Arch Surg 120:267-270, 1985.
Furthermore, topical antiseptic agents, which are known to be severe cytotoxins, impinge dramatically upon the wound-healing processes and greatly impair the host defense mechanism. Viljanto, "Disinfection of Surgical Wounds Without Inhibition of Normal Wound Healing", Arch Surg 115:253-256, 1980.
Alternatively, minute concentrations of silver ions in solution or in the wound environment demonstrate a pronounced micro-biocidal effect without the corresponding cytotoxic properties generally associated with antiseptic and other non-biocompatible agents used to facilitate wound antisepsis.
Wound healing is also influenced by other factors and interventional methods including the application of low amperage microcurrents. Clinical investigators have established that electro-stimulation can affect every phase of wound healing. Becker, R. "The Direct Current Control System: A Link Between Environment and Organism", N.Y. State, Med 62-1169-1176, 1962; Becker, R., "Electrical Control of Growth Processes", Med Times 95:657-669, 1967a,; and Becker, R. et al., "Method for Producing Cellular Differentiation by Means of Very Small Electrical Currents", Trans N.Y. Acad Sci 29:606-515, 1967b.
Direct galvanic or low intensity direct current delivered to the wound site, in a steady state or as pulsed electrical stimulation, at current intensities between 0 to 1000 microamperes increased adenosine triphosphate (ATP) levels and improved protein synthesis. Wolcott, L. et al., "Accelerated Healing of Skin Ulcers by Electrotherapy: Preliminary Clinical Result", South Med 62:795-801, 1969.
The process by which ATP synthesis occurs has been postulated by numerous investigators: Davis, R. V., "Therapeutic Modalities for the Clinical Health Sciences", 1st ed., 1983, Copyright, Library of Congress TXU-389-661; Griffin, J. E. et al., "Physical Agents for Physical Therapists", 2nd ed., Springfield, Charles C. Thomas, 1982; Krusen et al., "Handbook of Physical Medicine & Rehabilitation", 2nd ed., Philadelphia, W. B. Saunders Company, 1971: and Schriber W. A., "A Manual of Electrotherapy", 4th ed., Philadelphia, Lea & Feiblger, 1975.
In this process, electrons stimulated by microcurrents react with water molecules at the anode to produce positively charged hydrogen ions and in similar fashion, negatively charged hydroxyl ions are formed at the cathode. An electrical potential with a corresponding proton gradient is created between the anodic and cathodic poles, as well as between the cell wall of the tissue and intracellular fluid. When moving electrically charged hydrogen ions transverse the tissue cell wall and encounter the membrane of the mitochondria, (an intracellular organelle), with its stores of Adenosine triphosphatase, (the enzymatic catalyst of ATP production), the Adenosine triphosphatase is activated to enhance the manufacture of ATP. ATP is utilized as the energy resource for the endothermic synthesis of important proteins.
Amino acids, the building blocks of proteins, are transported by the electrical gradients through the mitochondrial membrane and synthesized into proteins by means of energy made available by ATP.
Physiological evidence of the biostimulatory effects of microcurrent application to wounds was reported by Alaverez, Om., et al., 1983, J. Invest. Dermatology, 81(2), 144, where they observed "a marked increase in the synthesis of collagen and the rate of epithelial regeneration, which are key aspects of wound healing".
In a carefully controlled in-vitro study, Nessler, J. P., Mass. O.P. Clinical Orth, Rel, Res., (217), 303 demonstrated that "transected rabbit tendons grown in culture medium responded to microcurrent stimulation of 7 uA with a 91% higher uptake of proline and 255% greater hydroxyproline activity, both of which are important biochemical constituents of tissue repair, than the unstimulated control".
Numerous other investigators have found that low intensity direct current enhanced the wound healing process. Carley, P. J. et al., 1985, Arch Phys Med Rehab, 66, (7), 443-446, described a "150-250% improvement in the rate of healing decubitus". Gault, W. et al., 1976, Physical Therapy, 56 (3) 265, "treated 106 ischemic skin ulcers with microcurrents which ranged from 200-800 uA and found that the ulcers treated healed twice as fast as those that were untreated". Wolcott, L. D. et al., 1969, South Med J., 62,796-801 "treated a group of 67 patients with low intensity direct electrical currents and reported an increased in the rate of healing over the control group. "
Electro-analgesis has been known for a number of years. Medical devices which are designed for the application of small electrical currents to the human body subscribe to the theory of Transcutaneous Electrical Nerve Stimulation (TENS) or Electro Galvanic Stimulation (EGS) to afford pain relief without the use of analgesic drugs which have a potential for patient misuse and habituation. In theory and practice, electrocurrents in micro- or milli-ampere range are applied to the body, through a pair of oppositely charged skin electrodes, which block the neuro-transmission of pain signals and/or reduce the perception of pain by directly influencing the release of endorphins, a natural analgesic produced endogenously. Goldstein, A., "Opid Peptides (Endorphins) in Pituitary and Brain", Science, 1976:193:1081-1086 and Guillenum, R., "Endorphins, Brain Peptides that Act like Opiates", N. Eng J Med 1977, 4:226-228.
Holloway, A. G., "Lower Leg Ulcers: An Overview", Chronic Wound Care: Health Management Publications, Inc., 1990, specifically states that "Characteristic symptoms of wounds classified as arterial ulcers generally involve pain."
Partial thickness wounds accompanied by inflammation and edema are uniformly painful. Experimentally, it has been proven that microampere electrical stimulation does mitigate pain secondary to tissue injury inasmuch as it has been shown that naloxone hydrochloride will block the palliative effects of the low level electrical stimulation by interfering with the opiate receptor sites in the brain. Sjolund, B. et al., "Electro Acupuncture and Endogenous Morphines", Lancet 1976:2:1085 and Hosobachi, Y. et al., "Pain Relief By Electrical Stimulation of the Central Gray Matter in Humans and Its Reversal by Naloxone", Science 1977:197:183-186.